Variable frequency tank circuit



March 13, 1951 L. N. HADLEY, JR 2,544,832

VARIABLE FREQUENCY TANK CIRCUIT Filed Aug. 8, 1945 2 Sheets-Sheet 1 PRIOR ART TIE-=4 Zjwumvfm Lawrence N. Hadlens Jr.

March 13, 1951 N. HADLEY, JR 2,544,832

VARIABLE FREQUENCY TANK CIRCUIT Filed Aug. 8, 1945 2 Sheets-Sheet 2 :ElErE ELLE-E.

MOTOR 0 (1T 41'! Rocat \onal Angle 6 Lawrence N; Hadleg Jr.

Patented Mar. 13, 1951 VARIABLE FREQUENCY TANK CIRCUIT Lawrence N. Hadley, Jr., Ann Arbor, Mich, assignor to the United States of America as represented by the Secretary of the Navy Application August 8, 1945, Serial No. 609,667

Claims. 1

This invention relates to ultra-high-frequency oscillation circuits particularly for use as ultrahigh-frequency tank circuits and in push-pull ultra-high-frequency oscillators.

This invention makes use of two parallel resonant-line oscillation circuits each in the form of a circular loop or a closed ring. In its broadest aspect, the invention comprises grid and plate tank units each formed of two spaced metal rings in parallel or juxtaposed relation, in a manner simulating parallel resonant lines, and connected together at opposing points by a common connector or permanent shorting bar. The rings of the grid tank unit at a point diametrically opposite the fixed shorting bar on each ring are connected individually to the control electrode of the push-pull tubes while the individual rings of the plate tank unit have separate connnection on each ring at a point diametrically opposite the fixed shorting bar to the anode or plate of the different tubes in push-pull. The fixed shorting bar in the grid tank unit is grounded while that of the plate tank unit is connected to some source of high voltage. Movable shorting bars or bridging members are-provided for tuning the respective tank units, each of said movable bridging members being slidable on both rings of the associated tank unit in a circular path, the bridging members being constructed and arranged for movement simultaneously and automatically into their respective adj ustedpositions.

It is accordingly an object of this invention to provide such an oscillation circuit which may be used in ultra-high-frequency oscillators and other high frequency radio equipment.

Another object of the invention is to provide an improved variable frequency tank circuit for use in ultra-high-frequency oscillators for eliminating key thump.

A further object of the invention is to provide tank oscillation circuits of circular loop form particularly adapted to ultra-high-frequencies.

Other objects, features and advantages of the invention will be apparent from the following particular description of a preferred embodiment thereof taken in connection with the accompanying drawing, in which:

Fig. 1 is a top plan view showing diagrammati cally a conventional parallel resonant line pushpull oscillator circuit in accordance with the prior art, the inclusion of this circuit being for the purpose of illustrating the extent of the improvement obtained by the present invention;

Fig. 2 is a diagrammatic view of the improved 2 oscillator circuit in accordance with the present invention;

Fig. 3 is an end view of the invention embodied in Fig. 2 showing diagrammatically the novel circular ring arrangement'of the parallel resonant lines and in which the inductance is varied by the use of circularly adjustable shorting bars or bridging members;

Fig. 4 illustrates diagrammatically a simple form of the loop tank circuit of the invention particularly for explaining the construction thereof; and

Fig. 5 is a graph of the output obtained from the oscillator disclosed in this invention.

Thus, referring to Fig. 1, which is a top plan view of a conventional parallel resonant-line push-pull variable frequency U.-H.-F. oscillator constructed in accordance with the prior art and is included for purposes of illustrating the improvement obtained by the improved parallel line oscillator tank circuit arrangement of the present invention as shown in Figs. 2 and 3 and theadvantages attendant thereto. In Fig. 1, a pair of triode tubes l0 and I2 are connected in pushpull relation. The grids l3 and M are connected to the conductors I5 and I6 of atransmission line i8. A slide bridge 19 is adjusted'on the line conductors I5 and I6 until a quarter wave length characteristic is obtained. The center 20 of the bridge i9 is grounded through a grid leak resistor.

2i. The cathodes 23 and 24 are also grounded,

' and they may be heated by any suitable source (not shown), Conductors 25 and 26 of a second transmission line 2'! are connected to the anodes or plates 28 and 29 of tubes l6 and I2 respectively. An adjustable bridging member 30 is connected to the transmission line conductors 25 and 26 at about a quarter wave length position at which the tuned-grid, tuned-plate circuit will cause oscillations. The center point -3l of the bridging member 30 is connected through a radio frequency choke 32 to the positive (B+) terminal of the anode current source (not shown) the negative terminal of which is grounded, all the above arrangements being in accordance with'the prior art practice .in the art.

Referring now to Figs. 2 and 3 which show the preferred embodiment of the invention as applied to an ultra-high-frequency oscillator circuit of thetuned grid tuned-plate type wherein each tuned circuit or tank unit comprises a pair of parallel inductance elements or line conductors in the form of juxtaposed continuous circular loops or metal rings formed of metal rods, of 1 similar size. The grid tank unit comprises ring members 40 and 4! connected together across opposed points by a fixed shorting bar or common conductive connector 42. The plate tank unit comprises the larger rings 44 and 45, of equal size, in juxtaposed relation connected together by a fixed shorting bar or common conductive connector '48. As illustrated 'infig. 4, the rings of the respective tank units are provided with suitable tabs 48, 49, 5D and 5! at points on the respective rings diammetrically opposite the point of attachment thereto :of the :fixed-shorting members. Individual connection is provided to connect the control grids 55 and :56 and the anodes or plates 5'! and 58 oi the push-pull-tri'odes heatedtype-for convenience-of illustration. The center points 65 of the fixed shorting bar 42 are grounded through grid leak resistor 66. "The ,center point t! of the fixed shorting bar '46 of the plate tank is connected to a suitable :source of high voltage. The rings of both tank units have their axesonthe same line'of centers so that a's'ha'ftlo 'towhich iscon'nected by arms and 12 the two movable shorting bars or bridging members 14 and 15 may be driven simultaneously in a suitable manner, as by means -'of electric motor 16,=to move the'bars'H and 1'5 in unison on therings of their respective tank units. The movable shortingbars and Here mounted in bridging relationship on their associated rings andthey areslidable thereon in a circular path into positions to accomplishthe desired irequency sweep.

Thus, the efiective line length which "the tubes '60 and 6'! see is then the length around'the circle in the "shortest direction 'to the moving shorting bars M and T5 in parallel with the length around the circle in the other direction to the fixed shorting bars 42 and 46. The output-from this oscillator system will be in accordance with the curve 80 in Fig. 5 wherein there is shown :a plot of frequency vs. rotational angle of the :movable shorting bars M and -15. It'will be apparent that for continuous sweeping there is a cyclic varying frequency in the oscillator output as evidenced by :no discontinuity in this curve hence, '-no key thump' to produce serious interference with communications outside the band of the transmitter.

While there has been described a preferred vices each having a cathode, an anode, and a "control element, a circuit interconnecting the control elements 'of both of 'said devices, said circuit including a pair of parallel closed ring conductors, and a common ground connection,

a sec'ond circuit interconnecting the anodes ei both of said devices, said second 'c'ircuit 'inc'lud- 4 ing a pair of parallel closed ring conductors, and a connection to a high voltage plate supply source, and means for tuning each of said circuits individually, said means comprising a pair of slidable bridging members, one associated with each of said circuits, arranged to be actuated in unison.

2. An oscillation generator having, in combination, a pairof electron discharge devices in push-pull ea'ch comprising cathode, "anode and control electrodes, four coaxial circular closed ring inductance elements disposed in parallel planes, two of said rings having a common conn-ecti'on and connecting together said anodes and the other two rings having a common connection :and connecting :together said control grids of said tubes, and apair of movable shorting members, one bridging across the grid inductance rings and the other bridging across the anode inductance rings, said shorting members being slidable in a circular path on and along their associated rings, and :means operatively connected to said ,-movable shorting members to :move them simultarieously onsaidrings.

3. In an oscillation generator, 'two vacuum tubes each having cathode, anode and control electrodes, an oscillation comprising two sets zof @parallel line conductors .each in the form of a continuous-metal ring-one set :to-form a grid tank and the other set a :plate tank, the rings of the grid :tank being individually connected at similar :points along their Fperipher-y to -the control electrode of a different tube and both rings being connected -'together atisecondipointby a common connection to groundtheringsof theplate :tank being individually connected at similar points along their peripheryto the anode'of a different tube and both rings-of :the .:plate tankbeing c0n- :nected together at a secondpoint :by a common connection to asource of high voltage.

4. In an oscillation circuit, two sets-of :parallel line inductances each in the form of a closed circle, one set to .form .-:a grid tank unit and the other :set a plate tank unitboth circular :in,- ductancesof each =tankbeing *connectedtogether by a common=connection,=two adjustablesbridging :members one across and slidableon the circular .inductances' of thegrid tank and the. other across and .slidable on the-circular inductances of the =p1at'e tan-k, said-bridging members. being :so constructed :and arranged as to -be..-mova'ble--simultaneously in a:circular path on the associatedinductances of. the respective tanks, two vacuum tubes having cathode, anode and control electrodes, the control electrodes of both tubes being connected separately to the individual inductanceswof the grid tankand the anodes of said tubesbeingconnected-separatelyto the:individual inductances oi. the :plate :tank, said grid tank being grounded and said plate tank being "corrnected to a source of high .potential.

5. In-a push-pull vacuum tube oscillationigenerator, ian oscilliationicircuit formed by w pairs of circular ring conductors :in spaced parallel relation, the two. rings of one pair or" conductors .beingiconnecteditogether at cppositezpointszacross from each other-and thence'toa commongroun'd, each ring thereof also beingaseparately connected to :the controliel'ectrodezof the.:push-.pull vacuum tubes at .aipoint on the ring 'diammetrically op- :positethe .p'ointzoi Ic'onnection -to ground, the two rings of the :other:pairofixconductors being C011?- n'ected together at opposite gpoints across from each conductor and. thence -ito a source of high voltages, feach ring also. being, separately iconnected to the anode of the diflerent vacuum tubes, and a movable shorting bar bridging each pair of rings and slidable thereon in a circular path.

LAWRENCE N. HADLEY, JR.

REFERENCES CITED The following references are of record in the file of this patent:

Number Segerstrom, Jr Jan. 23, 1945 

